1. Field of the Invention
The present invention generally relates to amorphous poly-alpha-olefin (APAO) hot melt adhesives. More particularly, it relates to improving the performance of amorphous poly-alpha-olefin hot melt adhesives for use in personal hygiene articles by the addition of high melt flow rate hydrogenated styrene block copolymers.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
U.S. Patent Publication No. 2014/0364532 A1, entitled “High Flow Hydrogenated Styrene-Butadiene-Styrene Block Copolymers and Applications,” describes a high melt flow, low viscosity, selectively hydrogenated styrene-butadiene-styrene (hSBS) or selectively hydrogenated controlled distribution styrene-butadiene/styrene-styrene (hSBSS) block copolymers, wherein the melt flow rate of said block copolymer is at least 100 g/10 min at 230° C. under 2.16 kg mass according to ASTM D1238. These block copolymers are said to have the highest melt flow rate of any styrenic block copolymer also possessing high strength and elasticity and to be useful in hot melt adhesives prepared from hSBS or hSBSS blended with polyalphaolefins, and elastic film, fiber, and nonwoven constructions using hSBS or hSBSS.
U.S. Pat. No. 5,302,675 to Sustic et al. and entitled “High Tensile Strength Amorphous 1-Butene/propylene Copolymers” discloses a process for the production of high tensile strength 1-butene/propylene copolymers by reacting 1-butene and propylene monomers in the presence of a catalyst system comprising: a) a solid supported catalyst component of the type commonly known as a Ziegler-Natta coordination polymerization catalyst; b) a trialkylaluminum co-catalyst component; and, c) an organo alkoxy silane component commonly referred to in the polyolefins industry as an external electron donor, or external donor. The butene-1/propylene copolymers have substantially improved mechanical and rheological properties which make them desirable for use in such applications as hot melt adhesives, sealants, coatings and similar applications.
The conventional use of hot-melt adhesives (HMAs) for elastic applications is based on heavily formulated styrene block copolymers (SBCs).